这是之前在ListView类中使用divider和dividerHeight参数实现的一个例子:
<ListView
android:id="@+id/activity_home_list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:divider="@android:color/transparent"
android:dividerHeight="8dp"/>
然而，在RecyclerView类中我没有看到这样的可能性。
<android.support.v7.widget.RecyclerView
android:id="@+id/activity_home_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical"/>
在这种情况下，是否可以定义边距和/或直接添加自定义分隔符视图到列表项的布局中，或者是否有更好的方法来实现我的目标?
使用RecyclerView itemdecoration -一个基本的分隔符样本在Kotlin android
一个完整的示例，包括一个构建器，添加边缘或使用资源颜色的可能性
class SeparatorDecoration constructor(ctx: Context, @ColorRes dividerColor: Int, heightDp: Float) :
RecyclerView.ItemDecoration() {
private val mPaints = Paint()
init {
mPaints.color = dividerColor
val thickness = TypedValue.applyDimension(
TypedValue.COMPLEX_UNIT_DIP,
heightDp,
ctx.resources.displayMetrics
)
mPaints.strokeWidth = thickness
}
override fun getItemOffsets(
outRect: Rect,
view: View,
parent: RecyclerView,
state: RecyclerView.State
) {
val params = view.layoutParams as RecyclerView.LayoutParams
// and add a separator to any view but the last one
val p = params.viewAdapterPosition
// and add a separator to any view but the last one
if (p < state.itemCount) outRect[0, 0, 0] =
mPaints.strokeWidth.toInt() // left, top, right, bottom
else outRect.setEmpty() // 0, 0, 0, 0
}
override fun onDraw(c: Canvas, parent: RecyclerView, state: RecyclerView.State) {
// we set the stroke width before, so as to correctly draw the line we have to offset by width / 2
val offset = (mPaints.strokeWidth / 2).roundToInt()
// this will iterate over every visible view
for (i in 0 until parent.childCount) {
// get the view
val view: View = parent.getChildAt(i)
val params = view.layoutParams as RecyclerView.LayoutParams
// get the position
val position = params.viewAdapterPosition
// and finally draw the separator
if (position < state.itemCount) {
c.drawLine(
view.left.toFloat(),
(view.bottom + offset).toFloat(),
view.right.toFloat(), (view.bottom + offset).toFloat(), mPaints
)
}
}
}
}
设置很简单。只需将您的装饰与其余的初始设置一起添加到您的recyclerView。
val decoration = SeparatorDecoration(context, R.color.primaryColor, 1.5f)
recyclerview.addItemDecoration(decoration)
我从一个旧的要点中分叉了DividerItemDecoration，并简化了它以适应我的用例，我还修改了它，以在ListView中绘制的方式绘制分隔符，包括在最后一个列表项之后的分隔符。这也会处理垂直的ItemAnimator动画:
1)将这个类添加到你的项目中:
public class DividerItemDecoration extends RecyclerView.ItemDecoration {
private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
private Drawable divider;
public DividerItemDecoration(Context context) {
try {
final TypedArray a = context.obtainStyledAttributes(ATTRS);
divider = a.getDrawable(0);
a.recycle();
} catch (Resources.NotFoundException e) {
// TODO Log or handle as necessary.
}
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
if (divider == null) return;
if (parent.getChildAdapterPosition(view) < 1) return;
if (getOrientation(parent) == LinearLayoutManager.VERTICAL)
outRect.top = divider.getIntrinsicHeight();
else
throw new IllegalArgumentException("Only usable with vertical lists");
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
if (divider == null) {
super.onDrawOver(c, parent, state);
return;
}
final int left = parent.getPaddingLeft();
final int right = parent.getWidth() - parent.getPaddingRight();
final int childCount = parent.getChildCount();
for (int i = 0; i < childCount; ++i) {
final View child = parent.getChildAt(i);
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
final int size = divider.getIntrinsicHeight();
final int top = (int) (child.getTop() - params.topMargin - size + child.getTranslationY());
final int bottom = top + size;
divider.setBounds(left, top, right, bottom);
divider.draw(c);
if (i == childCount - 1) {
final int newTop = (int) (child.getBottom() + params.bottomMargin + child.getTranslationY());
final int newBottom = newTop + size;
divider.setBounds(left, newTop, right, newBottom);
divider.draw(c);
}
}
}
private int getOrientation(RecyclerView parent) {
if (!(parent.getLayoutManager() instanceof LinearLayoutManager))
throw new IllegalStateException("Layout manager must be an instance of LinearLayoutManager");
return ((LinearLayoutManager) parent.getLayoutManager()).getOrientation();
}
}
2)添加装饰器到你的RecylerView:
recyclerView.addItemDecoration(new DividerItemDecoration(getActivity()));
如果有人只想在项目之间添加10dp的间距，你可以通过设置一个drawable到DividerItemDecoration来实现:
DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(
recyclerView.getContext(),
layoutManager.getOrientation()
);
dividerItemDecoration.setDrawable(
ContextCompat.getDrawable(getContext(), R.drawable.divider_10dp)
);
recyclerView.addItemDecoration(dividerItemDecoration);
其中，divider_10dpis一个可绘制资源，包含:
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
<size android:height="10dp"/>
<solid android:color="@android:color/transparent"/>
</shape>
